Fix netlink group mismatch in fds used for offload

Existing groups used for binding to netlink conntrack events don't
seem to work as expected. Fix this by using exact groups defined
in IOffloadConfig hal.

Test: as follows
      - Compiles and boots on walleye
      - Validated conntrack destroy events are received as expected.
      - Validated offload works as expected.

Bug:68018148
CRs-fixed:2126789

Change-Id: I76178fd7f109b82a4e4961347b8949937813d71d